Systems and methods for simulating contact between physical objects

ABSTRACT

The method generates a simulated object represented by finite elements each comprising two or more nodes that represent a first physical object, the first simulated object comprising a plurality of segments placed adjacent to each other to form a surface of the first simulated object. The method further includes generating a second simulated object. The method determines the distance between individual segments of the first simulated object and the plurality of segments of the second simulated object. The method determines a stiffness matrix and force vectors for the at least one segment of the first simulated object that is in contact with at least one segment of the second simulated object. The method transforms the stiffness matrix and the force vector from the segments to determine a stiffness matrix and a force vector on the two or more nodes of the finite element representation of the physical objects.

CROSS-REFERENCE TO RELATED PATENT APPLICATIONS

This application is a Continuation-In-Part of U.S. application Ser. No.13/625,807, filed Sep. 24, 2012, incorporated herein by reference in itsentirety.

BACKGROUND

Manufacturing complex systems and products usually include creatingcomputer-aided design models and conducting numerical tests on themodels to determine their behavior. Generating a functional model is atime-consuming process and reducing the amount of time for creating amodel and performing the simulation is beneficial to any productmanufacturer.

During the computer aided design (CAD) and/or computer-aided engineering(CAE) geometry modeling process, a user may wish to determine how two ormore shapes or bodies may interact with each other under external loadsas well as their resultant behavior.

SUMMARY OF THE DISCLOSURE

Embodiments of the methods and systems described herein performsimulation of structures such as pipes, beams, etc. to capture theirbehavior when they are in contact with each other or when they are incontact with either rigid or deformable bodies using the Finite ElementMethod (FEM). The objective of the numerical simulations is to determinethe deformed geometry, the reaction or contact forces between parts, thetransfer of state quantities (temperature, current, etc) and the strainsand stresses in the part to ensure safe, reliable and optimal partdesign. Pipes and beams and similar long and slender structures are usedin a variety of structures, such as but not limited to, CivilEngineering (Steel, Concrete and Wood Structures), AerospaceApplications (spars and struts in the wing and fuselage), Oil Industry(drilling and transportation), Automotive (bowden cable, wireharnesses), Energy Industry (piping systems, heat exchange systems,cables), Biomedical (stents, catheters), Materials Industry (wovencomposites, fabrics). Many of these applications require high levels ofaccuracy of solutions for safety of a properly designed system. Highlevels of accuracy can require more computational time and power ordecreased computational efficiency.

Embodiments of methods include generating a first simulated objectrepresented by one-dimensional beam finite elements, each of the finiteelements comprising two or more nodes that represent a first physicalobject, the first simulated object comprising a plurality of segmentsplaced adjacent to each other to form a surface of the first simulatedobject. The method further includes generating a second simulated objectthat represents a second physical object, the second simulated objectcomprising a plurality of segments placed adjacent to each other to forma surface the second simulated object. The method includes determiningthe distances between individual segments of the first simulated objectand the plurality of segments of the second simulated object. The methoddetermines whether contact exists based upon the distances. Upon adetermination that contact exists the method also calculates a stiffnessmatrix and force vectors for at least one segment of the first simulatedobject that is in contact with at least one segment of the secondsimulated object. The method includes converting the stiffness matrixand the force vector to determine a stiffness matrix and a force vectoron the two or more nodes.

Embodiments of the system includes a CAD/CAE computer system configuredto generate a first simulated object represented by finite elements eachcomprising two or more nodes that represent a first physical object, thefirst simulated object comprising a plurality of segments placedadjacent to each other to form a surface of the first simulated object.The CAD/CAE computer system is configured to generate a second simulatedobject that represents a second physical object, the second simulatedobject comprising a plurality of segments placed adjacent to each otherto form a surface of the second simulated object. A distancedetermination computer module is configured to determine the distancebetween individual segments of the first simulated object and theplurality of segments of either the first or the second simulatedobject. A stiffness matrix determination computer module is configuredto determine a stiffness matrix and force vectors for at least onesegment of the first simulated object that is in contact with at leastone segment of the second simulated object and the CAD/CAE systemconfigured to convert the stiffness matrix and the force vector from thesegments to determine a stiffness matrix and a force vector for the twoor more nodes of the finite element representation of the physicalobjects.

Embodiments of systems and method for simulating contact betweenphysical objects may be used for various types of systems. For example,mechanical systems, heat transfer systems, or electro-mechanical systemsmay be implemented using the embodiments of systems and method forsimulating contact between physical objects. In an example embodiment,all systems of cars, airplanes, wiring/cabling, piping, or heatexchanges may be simulated by the embodiments of the interactivesimulation and solver system.

BRIEF DESCRIPTION

FIGS. 1a and 1b are schematic drawings showing representations of atwo-node and three-node beam finite element.

FIG. 2 is a drawing of a set of object cross-sections.

FIG. 3a is a schematic perspective view drawing illustrating theorientation of a beam when the local y axis of the beam is in the globalz-y plane and parallel to global z axis.

FIG. 3b is a schematic perspective view drawing illustrating theorientation of a typical beam when the local y axis of the beam is inthe global z-y and rotated by 45 degrees.

FIG. 4a is a schematic perspective view drawing showing T beam that hasthe nodal location at the local origin of the beam.

FIG. 4b is a schematic perspective view drawing showing a T beam thathas the nodal location of the beam offset from the local orientation ofthe beam.

FIG. 5 is a flow diagram illustrating a process that may be implementedusing a computer system with a processor coupled to a non-transitorystorage medium in accordance with an exemplary embodiment.

FIGS. 6a and 6b are schematic drawings showing example representationsof two different objects in a two dimensional forms.

FIGS. 7a and 7b are schematic drawings showing an examplerepresentations of two different objects in a three dimensional forms.

FIG. 8 is a schematic drawing showing a three dimensional shellrepresentation of a curved object.

FIG. 9 is a flow diagram illustrating a process that may be implementedusing a computer system with a processor coupled to a non-transitorystorage medium in accordance with an exemplary embodiment.

FIG. 10 is a schematic perspective view drawing showing a threedimensional square cross-section beam in expanded mode according to anexample embodiment.

FIG. 11 is a schematic drawing illustrating a tube within a tubesegmentation.

FIG. 12 is a schematic drawing illustrating a tube within a tubesegmentation.

FIG. 13 is a schematic drawing illustrating Spline/Coons patch (dottedlines) representations of piece-wise linear segments (solid lines).

FIG. 14 is a schematic perspective view drawing illustrating two beamsin contact with each other, where ABCD are segment points.

FIG. 15 is a flow diagram illustrating a process that is used to analyzecontact between beams, pipes or other objects in accordance with anexemplary embodiment.

FIG. 16 is a schematic drawing showing auxiliary point locations on asegment.

FIG. 17 is a schematic drawing showing a pipe in pipe deformation.

FIG. 18 is a schematic drawing illustrating the contact force betweenpipes on contacting segments.

FIG. 19 is a schematic drawing illustrating the contact region of thecontacting segments from FIG. 18.

FIG. 20 is a flow diagram illustrating an exemplary process that mayperformed by a computer system with a process tied to a non-transitorymachine readable storage medium in accordance with an exemplaryembodiment.

FIG. 21 is a flow diagram of another exemplary process that may beimplemented on a computer system with a process tied to a non-transitorymachine readable storage medium in accordance with an exemplaryembodiment.

FIG. 22 is schematic block diagram of a computer system in accordancewith an exemplary embodiment.

DETAILED DESCRIPTION

The numerical simulation of beams and pipes are performed using threedimensional beam (3-D) elements in one embodiment. These elements asrepresented in FIGS. 1a and 1b and are geometrically represented byeither two or three nodes (e.g., nodes 1, 2, or 3), and these nodes inthe finite element sense are described by their three coordinatepositions X, Y and Z. Each node in FIG. 1a has six degrees of freedomUx, Uy, Uz, θx, θy, and θz. In certain formulations an additional degreeof freedom representing the twist is also represented. The numericalbehavior of these beams or pipes is governed by their shape functions.The technique described below is suitable for all three dimensionalbeam, pipe or other elements. Furthermore, these three dimensionalrepresentations are often simplified to represent two dimensional (2-D)beam or shell behavior. A user may simulate contact between two objectsby using a computer-aided design (CAD) geometry for use incomputer-aided engineering (CAE) modeling operations. The modelingoperations include, but are not limited to determining a point ofcontact between objects in one embodiment. A user may apply externalloads, prescribed motion, gravity, temperature or other externalexcitation on the objects.

FIG. 2 shows a typical set of object cross-sections. The objects may bea beam, pipe or shell cross-section. The objects may be a beam or pipecross-section. An important consideration on the modeling of beam andpipe elements is the cross sectional geometry. The long slenderstructures typically have beam cross-sections 200 shown in FIG. 2 andthese are typically called standard sections. The embodiments of thesystems and methods described here are not limited to the geometry ofthe sections shown in FIG. 2. FIG. 2 shows beam sections, such as butnot limited to T 201, channel 202, L 203, I 204, rectangular 205,trapezoid 206, solid circular 207, pipe 208, octagonal 209, elliptical210 and the like.

FIGS. 3a and 3b shows the modeling of beam or pipe elements that includea definition of the cross-section orientation of the cross section withrespect to the length and the global coordinate system (shown as x, y,and z). For each element along the part there is an orientation VE whichis a directional cosine with respect to the global coordinate system. Atthe nodal points 301 and 303 there may be multiple orientations basedupon the elements that are connected to the nodal points 301 and 303.The orientation of the beam cross section is used in the contactanalysis.

FIG. 4a shows a T beam 400 that has a central axial dimension thatconnects the nodes 401 and 403. FIG. 4b shows a T beam 450 that has alower axial dimension that connects the nodes 405 and 407. The beamoffset represents the distance between the beam origin (usually theshear center) and the nodal coordinate position. Additionally, thegeometric offset is utilized to construct the geometric representationof the contact surfaces. As shown in FIGS. 4a and 4b , the physicallocation of the beam is used in the subsequent calculation. In oneembodiment, the geometric representation used for contact will take intoaccount all four of these aspects of the beam, the coordinate positionof nodes of beam, beam cross section definition, cross sectionorientation and beam offsets.

FIG. 5 illustrates a process that may be implemented using a computersystem with a processor coupled to a non-transitory storage medium. Atblock 501, the system may determine contact information for objects thatare being simulated by using, for example, the distance formula. Also atblock 501, the system obtains the number of parts of the objects. In oneexample the objects may be colliding cars with a plurality of parts.Next, at block 501 the system determines whether a beam is representedin the CAD tool environment with a plurality of segments.

At block 503, data regarding each part of the object may be obtained.The data may indicate whether a part is deformable or rigid. The datamay be searched to indicate the deformable parts. The system candetermine if the part is represented in a segment form and the number offaces used to represent the part and whether outside, inside or combinedoutside/inside mode is being used to represent the part. At block 505,the system can search each part iteratively to determine boundaryinformation, element face and boundary node information for variousparts. Based on the determining the way a part is represented in thefigure, the system determines edges, faces or segments. An edge is aline that connects two nodes that represents the beam or pipe element oris on the perimeter of the element. The contact edges are the collectionof edges that enclose an object. A face is a region that bounds three ormore nodes on the perimeter of the element. The contact faces are thecollection of faces that enclose the volume of an object. A segment is abounded region that represents where contact may occur. For example, atblock 507, when a part is represented as a two dimensional part, theinformation regarding the edges of the part is determined. At block 509,when a part is an axisymmetric shell, the faces of the shell areconstructed. At block 511, when the part is represented as a beam andthe edges of the part are obtained. At block 513, when the part isrepresented in a three dimensional part, the faces of the threedimensional part are obtained. At block 515, the part is detected to berepresented as a three dimensional shell, the faces of the threedimensional shell are constructed. At block 517, if the part isrepresented as a beam element, then the part may be represented in anexpanded mode that comprises segments that combine to make the beamelement.

FIGS. 6a and 6b show an example representation of two different objects600 and 650 in a two dimensional form. In FIG. 6a a two dimensionalrepresentation of a portion of an object 600 is shown. Each node 601-618is associated with one or more quadrilateral elements is numbered withinthe portion of the object in one embodiment. The node pairs 601-602,602-603, 603-613, 613-618, 610-613, 618-617, 617-616, and 608-610, andare connected by edges. FIG. 6b is a two dimensional representationusing triangular elements. Each node 654-663 is associated with one ormore elements is numbered within the object 650 in FIG. 6b in oneembodiment. The nodes 654-655, 655-656, 656-657, 657-660, 659-660,659-658, 660-662, 662-661, 662-663, and 661-663 are connected by edges.

FIGS. 7a and 7b show an example representation of two different objects700 and 750 in a three dimensional representation. In FIG. 7a , asurface 710 is highlighted surrounded by 4 nodes (4, 5, 7 and 8). FIG.7b shows a highlighted surface 760 on the object 750 shown in threedimensional form. The highlighted portions of the objects 700 and 750shown in FIGS. 7a and 7b may be referred to as segments and the contactbetween the segments may be determined using the methods described inFIG. 5.

FIG. 8 shows a three dimensional shell representation of a curved object800. The segments 801, 802 and so on may be based on a projection of themid-surface of the shell based upon the surface normal, the thickness ofthe shell and the shell offset. The three dimensional shell shows thenodes 69 through 102 that form the mid-surface that is divided into aplurality of segments.

FIG. 9 illustrates a process that may be implemented using a computersystem with a processor coupled to a non-transitory storage medium. Theprocess from FIG. 9 may be used when a beam is divided into a pluralityof segments. At block 901, the process analyzes each node along a beamstructure to determine the averaged beam normal between segments. Atblock 903, the process may calculate the average normal at each node fora segment.

The average Normal may be determined using the following equations:

$V_{AVG}^{N} = {\frac{1}{c}{\sum\limits_{t = 1}^{c}V^{N_{E_{i}}}}}$

is the normal (direction cosine) at node N based upon element E_(i).

V_(AVG) ^(N) is the average normal at node N.

c is the number of elements that are associated with the node.

At block 905, the geometry of the beam may be determined. Next, a choicebetween blocks 907, 909, 911, and 913 may be made based on the modelthat is needed for the type of analysis. For example, when the object isdetermined to be a beam, the outside of the beam is segmented becausethe outside of the beam is used to determine contact with a beam atblock 907. When the object is determined to be a pipe, the outside ofthe pipe may be segmented at block 909. In another embodiment, theinside of a pipe may be segmented because the contact analysis requiresthe inside of a pipe at block 911. At block 913, both the inside and theoutside of the pipe may be segmented because they are relevant to thecontact analysis.

At block 915, the number of segments for the beam or pipe may bedetermined. The number of segments for standard beam cross sectionsgeometry may be determined using, for example, Table 1 below. Other waysof determining number of segments may be used as well.

TABLE 1 Geometry Number of segments T-section 8 Channel section 8L-Section 6 I-Section 12 Solid Rectangular 4 Solid Trapezoidal 4 SolidCircle 36 Pipe 1 or 2 times number of segments Solid Hexagonal 8 SolidElliptical 36

At block 917 the number of segments is determined based on table 1above. When a nonstandard beam is detected, at block 919, the beamsection information may be used. When a solid or elliptical circularbeam is detected, the number of segments may be determined based on thecircumference or diameter of the circular beam, at block 921. When theobject is a pipe, the number of segments multiplied by the number ofsides (inside and/or outside) may be used to generate the segments. Atblock 925, the number of determined segments may be created based on thebeam nodal coordinates, average nodal normal, and offset beam crosssection geometry.

As an example for a square beam 1000 with no offset a typical segment isshown in FIG. 10. The segments are based upon the type of cross-section(shown as box). A typical segment is arbitrarily labeled 1030, 1040,1050 and 1060. The labeling of the segment 1030, 1040, 1050 and 1060using the right hand rule indicates the normal of the outward directionof the segment. Also shown in on beam 1000 are the two nodes 1010 and1020.

FIGS. 11 and 12 illustrate a tube 1130 within a tube 1110 contactanalysis. A tube-in-tube analysis may require additional information todetermine which side the contact occurs (inside or outside). For theexpanded representation, an additional input to be provided may be wheninner faces, outer faces or both faces are needed for the contactanalysis. For determining content between a tube 1110 within a tube1130, the outer face 1132 of the inside tube 1110 and the inner face1114 of the outside tube 1110 may be segmented and analyzed. For beam tobeam contact the outer faces of the beams will be segmented andanalyzed. For determining contact of other shapes, both inner and outerfaces of hollow beams may be segmented and analyzed. This is shown inFIGS. 11 and 12 where in FIG. 11, contact segments are created on theboth the inner and outer surfaces of the pipe. However, in FIG. 12segments are created on the outer surface of the inner tube 1214 and theinner surface of the outer tube 1212 because those are the only facesthat will be in contact with each other when force is applied to theobject as a whole.

One may observe that for a circular beam or a curved pipe the segmentsare piecewise linear and hence do not exactly represent the curvature ofthe structure. This is relevant because the normal to the segment isused for the numerical calculations. To improve the accuracy of thecalculation a cubic spline and/or Coons patches may be used based uponthe coordinates of the corner points of the segment and the averagenormal at each corner point. As a circular pipe 1312 is represented by aquadratic surface, the Coons patches 1314 represent the geometry exactlyas shown in FIG. 13.

FIG. 14 shows two beams in contact with each other. In particular, beam1401 and beam 1403 are in contact with each other. A typical segment ofbeam 1401 defined by segment points labeled as ABCD can be defined suchthat the original position is (X1+V_(A)), (X2+V_(B)), (X2+V_(C)),(X1+V_(D)) where X1, X2 are the nodal positions of the original beamnodes and V_(A), V_(D) are the vectors from node 1 to A and D, andV_(B), V_(C) are the vectors from node 2 to B and C.

FIG. 15 shows a process that is used to analyze contact between beams,pipe or other objects. At step 1501, auxiliary points may be assigned tothe segments shown in FIG. 16. In one embodiment, the auxiliary pointmay represent the corners of the segment or points that define thesegment. At step 1503, distance between the auxiliary points of onesegment compared to the auxiliary points of another segment isdetermined. At step 1505, polylines (for two dimensional) or polygons(for three dimensional) are created based on the projection of segmentswhich are in close proximity with one another. At step 1507, a computersystem may determine if one polygon is in contact with another polygon.When the polygons are in contact with each other, at step 1509, astiffness matrix is calculated between the polygons that are in contactwith each other. At step 1511 friction is detected between the twopolygons. At step 1513, the polygon contribution of the stiffness matrixand force vectors to the segment points on the segment is calculated. Anexample method of calculating is discussed in greater detail below. Atstep 1515, the stiffness matrix and force vector are transformed fromsegment points to nodal points of the object using the Rigid BodyElement, (RBE2) method.

The implementation of the contact algorithm is based upon amending thestandard virtual work principal with two additional terms that governthe normal behavior and the tangential behavior, such that:

G(u, δ u) + ∫_(Γ) λ_(n)δ g_(n)dΓ + ∫_(Γ)l_(t)^(T)δ g_(t)dΓ = 0

Where u is the displacement field, δu are kinematically admissiblevariations of this field, Γ is that part of boundary of the bodies beingin contact and the subscript n is used to indicate the normal directionto the contact boundary, where the subscript t indicates the tangentialdirection. The function g_(n) is called a gap function and expresses thedistance between a point and its closest point projection on the contactboundary. The Lagrange multiplier λ_(n) represents the contact normalstress. Similarly, g_(t) is the tangential gap vector and I_(t) is thetangential stress vector. The tangential or frictional behavior isassumed to be governed by the Coulomb's friction model utilizing thecoefficient of friction μ such that:ϕ=∥I _(t)∥−μλ_(n)≤0

If g_(n)>0, a point is outside the contact boundary, if g_(n)=0, a pointis on the contact boundary and if g_(n)<0, a point would be beyond thecontact boundary, which is physically inadmissible.ϕ<0 corresponds to sticking and ϕ=0 corresponds to slipping.

The finite element system is solved with the conventional Newton-Raphsonmethod to achieve overall equilibrium and insure that the gap constraintis satisfied. Based on the iterative displacement solution obtained atiteration i, the following trial solutions for the Lagrange multipliersare introduced:λ_(n) ^(trial) =p _(n) ^(i−1) +E _(n) g _(n) ^(i);I _(t) ^(trial) =t _(t) ^(i−1) +E _(t) g _(t) ^(i)

In the above equations p_(n) and t_(t) are fixed estimates of λ_(n) andI_(t), E_(n) and E_(t) are penalty factors for the contact behavior inthe normal and tangential directions, and g_(n) and g_(t) follow fromthe global iterative displacement solution.

The auxiliary points discussed above basically define a local connectionbetween two contact segments. Indicating such a point by a subscript i,the gap function g_(ni) can be evaluated as the normal displacementdifference between a point and its closest point projection on thecontacted segment. Similarly, by looking at the tangentialdisplacements, the gap function g_(ti) can be evaluated. Thedisplacement of a point on a contact segment is a function of thedisplacements and (in case of shell elements) rotations of the nodescorresponding to that segment. By collecting all the nodal displacementand rotation degrees of freedom in a vector U, the gap functions can bewritten as:g _(ni)=(G _(ni) ^(T) −G′ _(ni) ^(T))Ug _(ti)=(G _(ti) ^(T) −G′ _(ti) ^(T))U

Here, vector G_(ni) and matrix G_(ti) express the dependency of thenormal and tangential displacements of a point on a contact segment onthe total set of degrees of freedom. In a similar way, and G′_(ni) andG′_(ti) are used for the closest point projection of this point on thecontacted segment.

It should be noted that, if applicable, these quantities also includethe effect of the shell thickness and shell offset vectors. Using theseexpressions and conventional variational calculus the contribution tothe force vector is given by:

${{\int_{\Gamma}{( \frac{\partial g_{n}}{\partial u} )^{T}\lambda_{n}d\;\Gamma}} + {\int_{\Gamma}{( \frac{\partial g_{t}}{\partial u} )^{T}l_{t}d\;\Gamma}}} = {{\sum\limits_{i = 1}^{N}{( {G_{ni}\  - \ G_{ni}^{\prime}} )\lambda_{ni}\Delta\Gamma_{i}}} + {\sum\limits_{i = 1}^{N}{( {G_{ti}\  - \ G_{ti}^{\prime}} )l_{ti}{\Delta\Gamma}_{i}}}}$

In the above equation N is the total number of auxiliary points λ_(ni)and I_(ti) are the estimated contact normal and tangential stresses inauxiliary point i and ΔΓ_(i) is the area corresponding to this point.

For sticking contact, the contribution to the global stiffness matrixis:

${{\int_{\Gamma}{( \frac{\partial g_{n}}{\partial u} )^{T}E_{n}\frac{\partial g_{n}}{\partial u}d\;\Gamma}} + {\int_{\Gamma}{( \frac{\partial g_{t}}{\partial u} )^{T}E_{t}\frac{\partial g_{t}}{\partial u}d\;\Gamma}}} = {\sum\limits_{i = 1}^{N}{( {G_{ni} - G_{ni}^{\prime}} ){E_{ni}( {G_{ni}^{T}\  - \ G_{ni}^{\prime\; T}} )}{{\Delta\Gamma}_{i}++}{\sum\limits_{i = 1}^{N}{( {G_{ti} - G_{ti}^{\prime}} ){E_{ti}( {G_{ti}^{T}\  - \ G_{ti}^{\prime\; T}} )}{\Delta\Gamma}_{i}}}}}$

For slipping contact the contribution to the global stiffness matrix is:

${{\int_{\Gamma}{( \frac{\partial g_{n}}{\partial u} )^{T}E_{n}\frac{\partial g_{n}}{\partial u}d\;\Gamma}} + {\int_{\Gamma}{( \frac{\partial g_{n}}{\partial u} )^{T}\mu\; E_{n}\frac{l_{t}^{T}}{l_{t}}\frac{\partial g_{t}}{\partial u}d\;\Gamma}} + {\int_{\Gamma}{( \frac{\partial g_{t}}{\partial u} )^{T}\frac{{\mu\lambda}_{n}}{l_{t}}{E_{t}\begin{bmatrix}{1 - \frac{\lambda_{t\; 1}^{2}}{{l_{t}}^{2}}} & \frac{{- \lambda_{t\; 1}}\lambda_{t\; 2}}{{l_{t}}^{2}} \\\frac{{- \lambda_{t\; 1}}\lambda_{t\; 2}}{{l_{t}}^{2}} & \frac{\lambda_{t\; 2}^{2}}{{l_{t}}^{2}}\end{bmatrix}}\frac{\partial g_{t}}{\partial u}d\;\Gamma}}}=={{\sum\limits_{i = 1}^{N}{( {G_{ni} - G_{ni}^{\prime}} ){E_{ni}( {G_{ni}^{T}\  - \ G_{ni}^{\prime\; T}} )}{\Delta\Gamma}_{i}}} + {\sum\limits_{i = 1}^{N}{( {G_{ni} - G_{ni}^{\prime}} )\mu\; E_{ni}\frac{l_{ti}^{T}}{l_{ti}}( {G_{ti}^{T}\  - \ G_{ti}^{\prime\; T}} ){{\Delta\Gamma}_{i}++}{\sum\limits_{i = 1}^{N}{( {G_{ti}\  - \ G_{ti}^{\prime}} )\frac{{\mu\lambda}_{n}}{l_{t}}{E_{t}\begin{bmatrix}{1 - \frac{\lambda_{t\; 1i}^{2}}{{l_{ti}}^{2}}} & \frac{{- \lambda_{t\; 1i}}\lambda_{t\; 2i}}{{l_{ti}}^{2}} \\\frac{{- \lambda_{t\; 1i}}\lambda_{t\; 2i}}{{l_{ti}}^{2}} & {1 - \frac{\lambda_{t\; 2i}^{2}}{{l}^{2}}}\end{bmatrix}}( {G_{ti}^{T}\  - \ G_{ti}^{\prime\; T}} ){\Delta\Gamma}_{i}}}}}}$

During the simulation a deformation may occur due to an applied load,boundary conditions and contact conditions such that the coordinateposition of nodes 1 and 2 are updated by the generalized nodaldisplacements (containing translations, rotations and other degrees offreedom as required) in the conventional manner such thatX1_(n+1)=X1_(n)+ΔU1. The subscript indicates time step n and ΔU is theincremental displacement of the step.

The updated coordinates of the segment points are governed by themulti-point constraint between nodes 1 and segment points A and D andthe one constraint between node 2 and segment points B and C. Thesegment ABCD of beam 1 is checked at various time intervals steps in theanalysis for contact with another beam patch, a shell patch, solid patchor a rigid body. A stiffness matrix will be formed between thesepolygons and included into the stiffness matrix associated with thesegments. The stiffness matrix represents a generalized spring that actsbetween the incremental displacements of segment points A, B, C, D, E,F, G, and H and the incremental internal force on these nodes. This canbe represented by the matrix equation.[K]*{du _(A) ,du _(B) ,du _(C) ,du _(D) ,du _(E) ,du _(F) ,du _(G) ,du_(H) }={f _(A) ,f _(B) ,f _(C) ,f _(D) ,f _(E) ,f _(F) ,f _(G) ,f _(H)}

In the equation above du_(A), du_(B), du_(C), du_(D), du_(E), du_(F),du_(G), and du_(H)} are the incremental displacements in globalcoordinate system of the segment points and{f_(A),f_(B),f_(C),f_(D),f_(E),f_(F),f_(G),f_(H)} is the internalforces. The stiffness matrix [K] and the force on segment A-B-C-D istransformed to beam nodes 1 and 2 and the stiffness and force associatedwith segment E-F-G-H are transformed to beam nodes 3 and 4 using theRBE2 constraint equations.

The result of the above calculations is that the stiffness matrix andforce vector on the conventional finite element degrees of freedom ofthe nodes. The stiffness matrices and force vectors are summed togetherwith other stiffness matrices and force vectors to be used in the finiteelement system. The solution is obtained using the conventional finiteelement methods to solve the linear set of equations. After stressrecovery and calculation of the forces one will obtain the desiredsolution. The solution includes an accurate determination of thedisplacement of the beams and/or pipes and the location of the contact.The displacement of the segments is obtained based upon the displacementof the nodes and the geometric information. The solution also includescontact forces between the beams and/or pipes with other beams and/orpipes or other deformable or rigid bodies. The solution may include theContact stresses between the beams and/or pipes with other beams and/orpipes or other deformable or rigid bodies. These quantities are obtainedbased upon the relative displacement of the segments, the stiffnessmatrix and the area of the segments.

The derivation in discussed above is not limited to structuraldisplacements, displacements and forces, but may be equally applied toother physical mechanisms such as but not limited to heat transfer,diffusion and electromagnetic analysis. In such problems the variable“u” referred to as displacement now refers to a generalized quantitysuch as temperature, the variable “K” referred to as stiffness matrix isa generalized operator and the variable “f” is a generalized load suchas flux. For a heat transfer problem, this stiffness matrix may includethe effects of conduction, convection and radiation.

FIG. 16 is a schematic drawing showing auxiliary points 1601, 1602,1603, 1604 and 1605 on a segment 1600. As shown in FIG. 16 the examplesegment has 4 corners 1601, 1602, 1603, 1604 and a center 1605. In thecase where the segment is circular, the segment may have a centerauxiliary point and an auxiliary point at the diameter.

To further demonstrate the above concepts a large deformation pipe inpipe simulation is shown in FIG. 17. Each pipe 1710 and 1720 isconstructed out of 20 beams with a pipe cross section. A load is appliedto the inner pipe at one end and the pipes are clamped on the other end.The deformed mesh of the pipe-in-pipe object 1700 is shown in FIG. 17.Also shown in FIG. 18 are the nodal force vectors 1730 from the contactand deformations. In one embodiment, the region of contact 1910 may bedisplayed in a different color as shown in FIG. 19. In anotherimplementation, the color of the region of contact 1910 may be adjustedto show the amount of force being exerted or the amount of frictionbetween the two pipes.

FIG. 20 is an example process that may performed by a computer systemwith a process tied to a non-transitory machine readable storage medium.The process includes steps 2001 to 2009. At step 2001, the systemgenerates a first simulated object represented by a beam finite elementeach comprising two or more nodes that represent a first physicalobject, the first simulated object comprising a plurality of segmentsplaced adjacent to each other to form a surface of the first simulatedobject. Next at step 2003, the system generate a second simulated objectthat represents a second physical object, the second simulated objectcomprising a plurality of segments placed adjacent to each other to forma surface of the second simulated object. Next at step 2005, theprocessor may determine the distance between individual segments of thefirst simulated object and the plurality of segments of the secondsimulated object. At step 2007, the system may determine a stiffnessmatrix and force vectors for the at least one segment of the firstsimulated object that is in contact with at least one segment of thesecond simulated object. At step 2009, the system may transform thestiffness matrix and the force vectors from the segments to determine astiffness matrix and a force vector on the nodes of the finite elementrepresentation of the physical objects.

FIG. 21 is another example process that may is implemented on a computersystem with a process tied to a non-transitory machine readable storagemedium. At step 2101, the system generates a geometric representation ofa first stimulated object that comprises a plurality of segments. Atstep 2103, the system may generate a second stimulated physical objectwith a region detected to be in contact with the first stimulatedobject. At step 2105, the system determines a stiffness matrix and forcevectors for a segment of the first simulated object that is in contactwith a segment of the second simulated object. At step 2107, thenumerical stiffness and force is transformed into nodal finite elementrepresentations.

Referring to FIG. 22, FIG. 22 is a schematic diagram of a dataprocessing system 2200 according to an embodiment. System 2200 includesa user input device 2202, CAD/CAE system 2210, display device 2220,processor 2230 and storage device 2240. The system 2200 may includeother devices such as network logic, wireless communication, printer andother known devices.

The input device 2202 as described herein may include a computer with amonitor, keyboard, keypad, mouse, joystick or other input devicesperforming a similar function. The input device 2202 may include akeyboard including alphanumeric and other keys, and may be coupled tothe bus for communicating information and command selections to theprocessor 2230. In one embodiment, the input device 2202 has a touchscreen interface or movement sensing interface that may be combinedwith, or separated from, display device 2220. The input device 2202 caninclude a cursor control device, such as a mouse, trackball, touchscreen, motion sensor or cursor direction keys, for communicatingdirection information and command selections to the processor 2230 andfor controlling cursor movement on the display device 2220.

The CAD/CAE system 2210 is a computer system that is in communicationwith the input device 2202, display device 2220, processor 2230 andstorage device 2240. In one implementation, the CAD/CAE system 2210 maybe stored on a non-transitory storage medium that is at the samelocation as the user input device 2202. In another implementation, theCAD/CAE system 2210 may be located in a different location than theinput device 2201. For example, the CAD/CAE system 2210 may communicatewith the input device 2202 through a network or wirelessly. Accordingly,the CAD/CAE system 2210 may be a cloud-based system that providessoftware as a service. In another embodiment, the CAD/CAE system 2210may include the processor 2230 and the storage device 2240.

The processor 2230 may be configured to receive instructions from theinput device 2202 and CAD/CAE system 2210. For example, the instructionsmay request the processor 2230 to create segments in 2212, calculate thedistance between two auxiliary points in 2215 and/or create stiffnessmatrices in 2216. The processor 2230 is configured to receive data fromand calculate results for each of the logics within the CAD/CAE system2210. The processor 2230 may be, but is not limited to being, an Intel®designed processor, AMD® designed processor, Apple® designed processor,QUALCOMM® designed processor, or ARM® designed process.

The storage device 2240 may include a memory such as a random accessmemory (RAM) or other dynamic storage devices. In anotherimplementation, the storage device 2240 may also include non-transitorystorage media that is configured to store information regarding thegeometric model and the finite element model that is being currentlymodified or was created in the past. The storage device 2240 may send orreceive data to or from the processor 2230 and each of the other systemsin the system 2210. For example, the storage device 2240 may beconfigured to communicate with the input device 2202, CAD/CAE system2210 and display device 2220. In one embodiment, the storage device 2240may be a remote storage device that stores the CAD/CAE system 2210 datain a different location than the input device 2202 or the CAD system2210. In another embodiment, the storage device 2240 may be located onthe same computer system as the input device 2202 and/or the CAD/CAEsystem 2210.

The CAD/CAE system 2210 is configured to provide a user with thefunctionality described below with respect to FIG. 1 through 21. TheCAD/CAE system 2210 includes a segmentation computer 2212, distancedetermination computer 2215, and stiffness matrix determination computer2216. The CAD/CAE system 2210 may receive the geometric modelinformation either from the user or from the storage device 2240. Insome implementations, a third party may provide the model information.Upon receiving the model information, the CAD/CAE system 2210 maydisplay the geometric model on the display device 2220. A user maychoose to edit the objects within a geometric model. The objects mayhave vertices and edges that connect the vertices.

The segmentation computer 2212 is configured to determine segments basedon the shape of the simulated object. The segmentation computer 2212 maydetermine the number of segments as discussed above with respect toFIGS. 1 through 21. Computer 2212 can be embodied as a module ofsoftware operating on one or more computer platforms.

The distance determination computer 2215 calculates the distance betweena plurality of segments. In one embodiment, the distance determinationcomputer 2215 determines the distance between an auxiliary point on asegment with auxiliary points of the opposing object on a continuousbasis. In another embodiment, the distance determination computer 2215warns the user that two objects are close enough to contact each other.Computer 2215 can be embodied as a module of software operating on oneor more computer platforms.

The stiffness matrix determination computer 2216 may calculate astiffness matrix based on the output determined by the distancedetermination computer 2215 as discuss above with respect to FIG. 1through 21. Computer 2216 can be embodied as a module of softwareoperating on one or more computer platforms.

In some embodiments, a method for simulation includes determining, basedon a 3-dimensional model, a line finite element geometricallyrepresenting a first simulated object. The first simulated object is apart of the model. The method further includes determining, based on themodel, a second element geometrically representing a second simulatedobject. The second simulated object is another part of the model. Inaddition, the method includes determining a physical interaction betweenthe first simulated object and second simulated object using at leastthe real geometry of the line finite element and second element withoutintroducing additional degrees of freedom for the line finite element.The physical interaction between the first simulated object and secondsimulated object is determined based on degrees of freedom associatedwith each of the two or more nodes of the line element. The secondelement is a line finite element, 3-dimensional finite element, or3-dimensional geometric element.

In some embodiments pertaining to structural simulations, each of thetwo or more nodes has 6 or 7 degrees of freedom. In some embodimentspertaining to heat transfer simulations or diffusion electrostaticsimulation, each of the two or more nodes has 1 degree of freedom. Insome embodiments pertaining to electromagnetic simulation, each of thetwo or more nodes has 4 or less degrees of freedom. In some embodiments,the first simulated object is a beam, pipe, wire, rod, or truss.

The detailed description set forth above in connection with the appendeddrawings is intended as a description of various aspects of the presentdisclosure and is not intended to represent the only aspects in whichthe present disclosure may be practiced. Each aspect described in thisdisclosure is provided merely as an example or illustration of thepresent disclosure, and should not necessarily be construed as preferredor advantageous over other aspects. The detailed description includesspecific details for providing a thorough understanding of the presentdisclosure. However, it will be apparent to those skilled in the artthat the present disclosure may be practiced without these specificdetails. In some instances, well-known structures and devices are shownin block diagram form in order to avoid obscuring the concepts of thepresent disclosure. Acronyms and other descriptive terminology may beused merely for convenience and clarity and are not intended to limitthe scope of the present disclosure.

While for purposes of simplicity of explanation, the methodologies areshown and described as a series of acts, it is to be understood andappreciated that the methodologies are not limited by the order of acts,as some acts may, in accordance with one or more aspects, occur indifferent orders and/or concurrently with other acts from that shown anddescribed herein. For example, those skilled in the art will understandand appreciate that a methodology could alternatively be represented asa series of interrelated states or events, such as in a state diagram.Moreover, not all illustrated acts may be required to implement amethodology in accordance with one or more aspects.

Embodiments of the subject matter and the operations described in thisspecification can be implemented in digital electronic circuitry, or incomputer software, firmware, or hardware, including the structuresdisclosed in this specification and their structural equivalents, or incombinations of one or more of them. Embodiments of the subject matterdescribed in this specification can be implemented as one or morecomputer programs, i.e., one or more modules of computer programinstructions, encoded on computer storage medium for execution by, or tocontrol the operation of, data processing apparatus. Alternatively or inaddition, the program instructions can be encoded on an artificiallygenerated propagated signal, e.g., a machine-generated electrical,optical, or electromagnetic signal, which is generated to encodeinformation for transmission to suitable receiver apparatus forexecution by a data processing apparatus. A computer storage medium canbe, or be included in, a computer-readable storage device, acomputer-readable storage substrate, a random or serial access memoryarray or device, or a combination of one or more of them. Moreover,while a computer storage medium is not a propagated signal, a computerstorage medium can be a source or destination of computer programinstructions encoded in an artificially generated propagated signal. Thecomputer storage medium can also be, or be included in, one or moreseparate physical components or media (e.g., multiple CDs, disks, orother storage devices).

The operations described in this specification can be implemented asoperations performed by a data processing apparatus on data stored onone or more computer-readable storage devices or received from othersources.

The term “logic”, “data processing apparatus” or “computing device”encompasses all kinds of apparatus, devices, and machines for processingdata, including by way of example a programmable processor, a computer,a system on a chip, or multiple ones, or combinations, of the foregoing.The apparatus can include special purpose logic circuitry, e.g., an FPGA(field programmable gate array) or an ASIC (application specificintegrated circuit). The apparatus can also include, in addition tohardware, code that creates an execution environment for the computerprogram in question, e.g., code that constitutes processor firmware, aprotocol stack, a database management system, an operating system, across-platform runtime environment, a virtual machine, or a combinationof one or more of them. The apparatus and execution environment canrealize various different computing model infrastructures, such as webservices, distributed computing and grid computing infrastructures.

A computer program (also known as a program, software, softwareapplication, script, or code) can be written in any form of programminglanguage, including compiled or interpreted languages, declarative orprocedural languages, and it can be deployed in any form, including as astandalone program or as a module, component, subroutine, object, orother unit suitable for use in a computing environment. A computerprogram may, but need not, correspond to a file in a file system. Aprogram can be stored in a portion of a file that holds other programsor data (e.g., one or more scripts stored in a markup languagedocument), in a single file dedicated to the program in question, or inmultiple coordinated files (e.g., files that store one or more modules,sub programs, or portions of code). A computer program can be deployedto be executed on one computer or on multiple computers that are locatedat one site or distributed across multiple sites and interconnected by acommunication network.

The processes and logic flows described in this specification can beperformed by one or more programmable processors executing one or morecomputer programs to perform actions by operating on input data andgenerating output. The processes and logic flows can also be performedby, and apparatus can also be implemented as, special purpose logiccircuitry, e.g., an FPGA (field programmable gate array) or an ASIC(application specific integrated circuit).

Processors suitable for the execution of a computer program include, byway of example, both general and special purpose microprocessors, andany one or more processors of any kind of digital computer. Generally, aprocessor will receive instructions and data from a read only memory ora random access memory or both. The essential elements of a computer area processor for performing actions in accordance with instructions andone or more memory devices for storing instructions and data. Generally,a computer will also include, or be operatively coupled to receive datafrom or transfer data to, or both, one or more mass storage devices forstoring data, e.g., magnetic, magneto optical disks, or optical disks.However, a computer need not have such devices. Moreover, a computer canbe embedded in another device, e.g., a mobile telephone, a personaldigital assistant (PDA), a mobile audio or video player, a game console,a Global Positioning System (GPS) receiver, or a portable storage device(e.g., a universal serial bus (USB) flash drive), to name just a few.Devices suitable for storing computer program instructions and datainclude all forms of non volatile memory, media and memory devices,including by way of example semiconductor memory devices, e.g., EPROM,EEPROM, and flash memory devices; magnetic disks, e.g., internal harddisks or removable disks; magneto optical disks; and CD ROM and DVD-ROMdisks. The processor and the memory can be supplemented by, orincorporated in, special purpose logic circuitry.

To provide for interaction with a user, embodiments of the subjectmatter described in this specification can be implemented on a computerhaving a display device, e.g., a CRT (cathode ray tube) or LCD (liquidcrystal display) monitor, for displaying information to the user and akeyboard and a pointing device, e.g., a mouse or a trackball, by whichthe user can provide input to the computer. Other kinds of devices canbe used to provide for interaction with a user as well; for example,feedback provided to the user can be any form of sensory feedback, e.g.,visual feedback, auditory feedback, or tactile feedback; and input fromthe user can be received in any form, including acoustic, speech, ortactile input. In addition, a computer can interact with a user bysending documents to and receiving documents from a device that is usedby the user; for example, by sending web pages to a web browser on auser's client device in response to requests received from the webbrowser.

Embodiments of the subject matter described in this specification can beimplemented in a computing system that includes a back end component,e.g., as a data server, or that includes a middleware component, e.g.,an application server, or that includes a front end component, e.g., aclient computer having a graphical user interface or a Web browserthrough which a user can interact with an implementation of the subjectmatter described in this specification, or any combination of one ormore such back end, middleware, or front end components. The componentsof the system can be interconnected by any form or medium of digitaldata communication, e.g., a communication network. Examples ofcommunication networks include a local area network (“LAN”) and a widearea network (“WAN”), an inter-network (e.g., the Internet), andpeer-to-peer networks (e.g., ad hoc peer-to-peer networks).

The computing system can include clients and servers. A client andserver are generally remote from each other and typically interactthrough a communication network. The relationship of client and serverarises by virtue of computer programs running on the respectivecomputers and having a client-server relationship to each other. In someembodiments, a server transmits data (e.g., an HTML page) to a clientdevice (e.g., for purposes of displaying data to and receiving userinput from a user interacting with the client device). Data generated atthe client device (e.g., a result of the user interaction) can bereceived from the client device at the server.

While this specification contains many specific implementation details,these should not be construed as limitations on the scope of anyinventions or of what may be claimed, but rather as descriptions offeatures specific to particular embodiments of particular inventions.Certain features that are described in this specification in the contextof separate embodiments can also be implemented in combination in asingle embodiment. Conversely, various features that are described inthe context of a single embodiment can also be implemented in multipleembodiments separately or in any suitable subcombination. Moreover,although features may be described above as acting in certaincombinations and even initially claimed as such, one or more featuresfrom a claimed combination can in some cases be excised from thecombination, and the claimed combination may be directed to asubcombination or variation of a subcombination.

Similarly, while operations are depicted in the drawings in a particularorder, this should not be understood as requiring that such operationsbe performed in the particular order shown or in sequential order, orthat all illustrated operations be performed, to achieve desirableresults. In certain circumstances, multitasking and parallel processingmay be advantageous. Moreover, the separation of various systemcomponents in the embodiments described above should not be understoodas requiring such separation in all embodiments, and it should beunderstood that the described program components and systems cangenerally be integrated together in a single software product orpackaged into multiple software products.

Thus, particular embodiments of the subject matter have been described.Other embodiments are within the scope of the following claims. Forexample, while certain embodiments have been described with respect tosearching of a single media type, i.e., image search or video search,one or more embodiments are also relevant to a generic search where thesearch results are blended with different media types. Thus, forexample, a user can type in a keyword search phrase into an Internetsearch engine and obtains results that contain images, video and othermedia types blended with text results, and in which relevant matchingadvertisements are obtained (and provided to the user) that match one ormore of these multi-media search results. In some cases, the actionsrecited in the claims can be performed in a different order and stillachieve desirable results. In addition, the processes depicted in theaccompanying figures do not necessarily require the particular ordershown, or sequential order, to achieve desirable results. In certainimplementations, multitasking and parallel processing may beadvantageous.

What is claimed is:
 1. A method, comprising: determining, by a computeraided design (CAD)/computer-aided engineering (CAE) computer systembased on a 3-dimensional computer model, a line finite elementgeometrically representing a first simulated object, wherein the firstsimulated object is a part of the model; determining, by the CAD/CAEcomputer system, based on the 3-dimensional computer model, a secondelement geometrically representing a second simulated object, whereinthe second simulated object is another part of the model; and performingnumerical simulation, by the CAD/CAE computer system, to determine aphysical interaction between the first simulated object and secondsimulated object based on at least a real geometry of the line finiteelement and the second element without introducing additional degrees offreedom for each node of the line finite element.
 2. The method of claim1, wherein the line finite element comprises two or more nodes.
 3. Themethod of claim 2, wherein: for structural simulation, each of the twoor more nodes has 6 or 7 degrees of freedom; for heat transfersimulation or diffusion electrostatic simulation, each of the two ormore nodes has 1 degree of freedom; and for electromagnetic simulation,each of the two or more nodes has 4 or less degrees of freedom.
 4. Themethod of claim 2, wherein the physical interaction between the firstsimulated object and second simulated object is determined based ondegrees of freedom associated with each of the two or more nodes of theline finite element.
 5. The method of claim 1, wherein the firstsimulated object is a beam, pipe, wire, rod, or truss.
 6. The method ofclaim 1, wherein the second element is a line finite element,3-dimensional finite element, or 3-dimensional geometric element.
 7. Themethod of claim 1, wherein the physical interaction comprisesdetermining one or more of structural displacement, heat transfer,diffusion, or electromagnetic analysis.
 8. A non-transitorycomputer-readable medium containing computer-readable instructions suchthat, when executed by a processor of a computer aided design(CAD)/computer-aided engineering (CAE) computer system, cause theprocessor to: determine, based on a 3-dimensional computer model, a linefinite element geometrically representing a first simulated object,wherein the first simulated object is a part of the model; determining,by the CAD/CAE computer system, based on the 3-dimensional computermodel, a second element geometrically representing a second simulatedobject, wherein the second simulated object is another part of themodel; and performing numerical simulation, by the CAD/CAE computersystem, to determine a physical interaction between the first simulatedobject and second simulated object using computer simulation based on atleast a real geometry of the line finite element and the second elementwithout introducing additional degrees of freedom for each node of theline finite element.
 9. The non-transitory computer-readable medium ofclaim 8, wherein the line finite element comprises two or more nodes.10. The non-transitory computer-readable medium of claim 9, wherein: forstructural simulation, each of the two or more nodes has 6 or 7 degreesof freedom; for heat transfer simulation or diffusion electrostaticsimulation, each of the two or more nodes has 1 degree of freedom; andfor electromagnetic simulation, each of the two or more nodes has 4 orless degrees of freedom.
 11. The non-transitory computer-readable mediumof claim 9, wherein the physical interaction between the first simulatedobject and second simulated object is determined based on degrees offreedom associated with each of the two or more nodes of the line finiteelement.
 12. The non-transitory computer-readable medium of claim 8,wherein the first simulated object is a beam, pipe, wire, rod, or truss.13. The non-transitory computer-readable medium of claim 8, wherein thesecond element is a line finite element, 3-dimensional finite element,or 3-dimensional geometric element.
 14. The non-transitorycomputer-readable medium of claim 8, wherein the physical interactioncomprises determining one or more of structural displacement, heattransfer, diffusion, or electromagnetic analysis.
 15. A computer aideddesign (CAD)/computer-aided engineering (CAE) computer system,comprising: a computer-implemented storage medium; and a processorcoupled to the computer-implemented storage medium, configured to:determine, based on a 3-dimensional computer model, a line finiteelement geometrically representing a first simulated object, wherein thefirst simulated object is a part of the model; determining, by theCAD/CAE computer system, based on the 3-dimensional computer model, asecond element geometrically representing a second simulated object,wherein the second simulated object is another part of the model; andperforming numerical simulation, by the CAD/CAE computer system, todetermine a physical interaction between the first simulated object andsecond simulated object using computer simulation based on at least areal geometry of the line finite element and the second element withoutintroducing additional degrees of freedom for each node of the linefinite element.
 16. The system of claim 15, wherein the line finiteelement comprises two or more nodes.
 17. The system of claim 16, whereinfor structural simulation, each of the two or more nodes has 6 or 7degrees of freedom; for heat transfer simulation or diffusionelectrostatic simulation, each of the two or more nodes has 1 degree offreedom; and for electromagnetic simulation, each of the two or morenodes has 4 or less degrees of freedom.
 18. The system claim 15, whereinthe physical interaction between the first simulated object and secondsimulated object is determined based on degrees of freedom associatedwith each of two or more nodes of the line finite element geometricallyrepresenting the first simulated object.
 19. The system of claim 15,wherein the first simulated object is a beam, pipe, wire, rod, or truss.20. The system of claim 15, wherein the second element is a line finiteelement, 3-dimensional finite element, or 3-dimensional geometricelement.